Dop or holder for diamonds and like tool pieces for grinding or polishing purposes



` 2,394,242 TOOL PIECES POSES v Feb. L5, 1946. F, c. JEARUM DOP OR HOLDER FOR DIAMONDS AND LIKE FOR GRINDING OR PO ING PUR LISH lf'i led Npv., 17,

Patented Feb. 5, 1946 DOP OR HOLDER FOR DIAMONDS AND LIKE TOOL PIECES VFOR GRINDING OR POLISH- ING PURPOSES Frederick Charles Jearum, Sutton, England Application November 17, 1943, Serial No. 510,679

' In Great Britain November 19, 1942 4- Claims.

This invention relates to dops or holdersfor diamond or other percious stone tool pieces or other tool pieces or tips of hard metal for grinding or polishing purposes in generating or shaping the diamond or other tool piece or tip, of the kind known as mechanical dops or holders, in contradistinction to those wherein the tool piece or tip is secured by cement or solder.

' The aim of the present invention is to provide a mechanical dop or holder (for diamonds or other minerals or hard metals, hereinafter referred to as stones) in which the holding or securing means can be readily adapted to con? form to any particular shape or angle (such as the wedge angle of stones of wedge shape in plan) of the various shapes or angles possessed by stones to be operated upon without having to resort to machining or other accurate method of shaping the seating for the stone position.

The invention consists in a dop or holder of the character described comprising: a base member having at the forward end a fiat bed for receiving and presenting the stone for grinding, polishing or the like to a lapping disc and having a, longitudinalchannel in rear of said bed, a backing device consisting of three or more parallel strips relatively slidable longitudinally in said channel to position their forward ends for engagement with the rearward shape of the stone as viewed in plan to locate it laterally and longitudinally on said bed, means operating laterally on said backing strips for clamping them in any adjusted position on said base member and a clamping member adapted to bear upon the upper side of the stone to secure it upon said bed.

The invention also consists in a dop or holder as set forth in the preceding paragraph wherein thebacking strip device comprising a set of three strips has the ends of its outer'strips shaped to engage the rearward facets of the stone, the end of the middle strip being engageable with the rearward extremity of the stone.

Theinvention further consists in a dop or holder wherein the backing device comprises a group of more than three strips having rounded forward ends and being sufiicient in number such that the rounded ends define the outline of the rear adjacent part of theqstone making a series of closely spaced .contacts therewith when such strips are advanced along said channel for lo. eating the stone laterally and longitudinally on said bed. v

Further features of the invention will be hereinafter described and defined in the claims.

In the accompanying drawing which illustrates several examples of modes of carrying the invention into effect, y Figure 1 is a side elevation of a dop according to the invention.

Figure 2 is a plan view according to Figure 1 with the cover plate and clamping member for the upper side of the stone removed.

Figure 3 is a plan view of one form of backing device strips assembled together side by side for employment in any of the forms of dop described in the specification.

Figure 4 is a side elevation f a modied form of dop or holder.

Figure 5 is a longitudinal sectional view of the dop shown in Figure 4, while Figure 6 is a plan view thereof with the cover plate removed. Y Y Figures '7 and 8 are respectively a plan and elevation of a cover plate and conicallocking plug described in reference to the form ofthe invention shown in Figure 4. l

Figure 9 -is a. plan View of a modified form of dop While Figure 10 is a plan view of a modied form of base member for a dop according to the invention.

Figure 11 is a front end View of the base member seen in Figure 10, and

Figure 12 is'a perspective View of a wedge or chisel-shaped form of stone.

In carrying the invention into eiect according to one form as described by way of example (see Figures 1 and 2) a base member l is provided with a at bed or support la for the stone. This bed or support may bea plain superices parallel with the bottom plane of the base (as `seen in Figure 1) or at an angle thereto. On each side the base is provided with a longitudinal flange Ib to vafford a parallel-walled channel in rear ofthe position at which the stone is received upon the bed. A coverplate 2 is provided for the channel and is secured by set screws 2a, the bed I a, the side iianges I b and the cover plate 2 thus forming a tunnel for the reception of a backing device generally designated 3' adapted to slide longitudinally within the tunnel. One of the flanges I b and the corresponding side of the base is provided with a recess to receive a clamping jaw or foot 3 which is carried on a set screw or a bolt device such as 3a so as to bring pressure to bear upon the sides of the backing device to lock or clamp such in position afterv adjustment. The forward p art of thebase (in plan) is angular or bevelled to afford an appropriate grinding clearance and in elevation at the to form a cup or cage 5a for'the rear of a ball 5b carried on a stem 5c which is located in the end of th'e clamping lever 4. This arrangement provides a clamping device which automatically adjusts itself to the inclination of the Wedge shape (in vertical sectional elevation) or other form of the stone under treatment.

The backing device may comprise three parallel'strips of metal a, b and c (see Figure 8) the front ends of the outer ones a andbeoi which are inwardly bevelled to an angle roughly corresponding with that of the mean angles of the wedges o f stones likely to be met with. The middle strip c `may have a square or concave end and is adapted to engage the extremity ofY the stonefor be set back to accommodate its pointed end.A Strips such as c may be provided in several widths for use with the outer strips c and b according to the rear face of the shank or back of the stone. Alternatively the side pieces c and b may have convex surfaces as viewed in plan the chord of which roughly corresponds with the mean angle of the wedge shapes it is adapted. to accommodate. The convex forno will, it will be appreciated, provide a line contact for a considerable variety of angles of wedge. In Figure 3 the three strips a. D ande are seen tted together for insertion upon' the bed lc and 'beneath the cover plate 2 in place of the arrangement shown in Figure l.

In setting up, a stone is positioned to protrude over the forward end of the base in the usual manner. The side strips oi the backing device are then pushed forward in the tunnel until they engage the facets of the wedge of the rear of. the stone.V :The centre strip is th'en pushed forward to act as an abutment for the rear extremity of the stone. When the stone hasthus been lateral- 1y and longitudinally located in position, the side clamping law is screwed tight to prevent the backing device from moving and the linger described above is then positioned with its rounded tip upon the top surface ofthe stone and the set screw .screwed down to clamp the stone iirmly upon the bed. It will be observed that the side pieces, which need not fit the stone with absolute accuracy, may be readily. led, if necessary, to

backing device in the adjusted position. The

flanges lb of the base element are formed with undercutor dovetail longitudinal grooves and the cover plate 2' (Figure 7) has bevelled longitudinal edges so that the cover plate may be slid into position in the grooves. The cover plate has lugs 2b' `in which is pivoted a stone clamping lever 4 having a downwardly turned front end linger and an abutment screw 2c' at the rear for bringing clamping pressure to bear upon th'e stone. Alternatively -the lever may have a ball-jointed foot of the kind described in reference to Figure 1.

The channel bed la' and the adjacent side walls have a conical cavity or bore E into which a locking plug of conical shape 1 is adapted to justed positions.

lit. The plus 'l has a channel 'la cut across its upper surface to correspond with the channel la so as to provide wings 1b for engaging the sides of the backing device and clamping such in ad- The plug has a vertical slit or is slotted as at 'lo to enable the wings la to approach one another to produce the clamping pressure.

The body of the conical plug has a tapered bore 'ld for receiving the taper or wedge-shaped end of a locking spindle 8 which is screwthreaded 'at `8a at its outer end and terminates with a milled operating head 8b. The spindle 8 is adapted to enter the longitudinal bore lc in the base member I and the screwthreaded, portion engagethe shape of any particular stone to be y ground.

The `backing device 3', Fig. 2, may be said to comprise a group (for example seven or eight) of thin strips of metal or wire pieces d of round or square cross section which are slidable in the channel between the danses lb and under the cover platev v2, The strips are preferably formed with rounded stcne-ensagingends. In this form, when the stone has been seated and held in position by the clamping device, each of the backing strips' or wires in turn is pushed forward to cause them individually to contact with the rear face ci the stone so that when all the strips have been pushed forward the number employed iS such-that their ends correspond with or define of the stone, making a series of closely spaced line 8a is adapted to engage the internal screwthread ld. When the spindle is advanced forwardly through the bore lc its tapered end which is normally out of coaxial alignment with the tapered bore 'ld inthe plug 1. pulls the latter downwardly in its conical cavity and thus causes the wings la to approach one another and operate with a clamping action on the backing device. When the spindle is retracted the resilience afforded by the slotted form of the plug causes the clamping pressure of the wings 1b to be relieved.

'I 'he-bed la' may be provided with a backing device in anyrof the single or multiple forms described above with reference to Figures 1 and 3. In Figure 9 is illustrated a modified shape of basemember l" ntted with a cover plate 2 such as already described, a conical locking device 6 and operating spindle 8 as described above in reference to Figures 4 to 8. This form of the.

invention is adapted more particularly for cutting, `grinding and polishing the anks or shank walls of a stone and hence the front face of the member I" may be rectilinear. The backing device may comprise a series of strip members of the character such as shown in Figure 3 or it may comprise a considerable number of narrow strips d suchV as illustrated in Figure 2 which may be adjusted so that their forward ends outline the shape of the flanks or side surfaces and a part of the bevelled tip of the stone to be treated.

In Figures l0 and ll are illustrated a modiiication of the bed l'" for accommodating stones the base or under surface of which is of wedge or chisel Shape Such as seen in enlarged form in Figure .112.. In this case the iorward portion of vthe bed la'" is provided with a groove le of v shape in cross section in which the wedge of a diamond (Figure 12) is seated. Also the flanges Ib'" are provided with dovetailed grooves for accommodating the bevelled edges of a cover plate. Otherwise' the base member shown in Figures and 11 may be of similar construction and is adapted to receive a cover plate and backing device locking means similar t9 those already described.

The forward portion or nose of the various base members described above may be bevelled (in plan) to a minimum angle suitable for the accommodation of stones of a range of angles or a series of base members may be made with different nose angles such as seen in Figures 2, 6 and 10, to suit the angles of the various stones to be treated.

The various base members described above may be secured upon a dop holding arm or feed or other support in any suitable manner, for example, the base members may have a screwthreaded cavity such as If shown in Figure 1 adapted to be engaged by a set screw carried. by the dop arm or support to attach the base members in position thereon.

It is to be understood that the several modifications described in reference to particular iigures may ybe applied to the invention described in connection with other figures or forms.

I claim:

l. A dop or holder of the character described comprising: a base member having at the forward end a flat bed for receiving and presenting the stone for grinding, polishing or the like to a lapping disc and having a longitudinal channel in rear of said bed, a backing device consisting of three or more parallel strips relatively slidable longitudinally in said channel to position their forward ends for engagement with the rearward shape of the stone as viewed in plan to locate it laterally and longitudinally on said bed, means operating laterally on said backing strips for clamping them in any adjusted position on said base member, a cover removably mounted on the base member and overlying the channel to form a tunnel through which the backing strips are slidable and a clamping member adapted to bear upon the upper side of the stone to secure it upon said bed.

2. A dop or holder as claimed in claim 1, wherein clamping means for the backing strips comprise: a split conical plug having a through way aperture for receiving the conical end of a spindle and having wings forming a short channel for engaging the sides of the outer of the backing strips; a conical seating in the base channel for the plug and a longitudinally displaceable screwthreaded vspindle having a tapered end for entering the aperture in the plug and drawing it into its seating to clamp the wings laterally upon the strips.

3. A dop or holder as claimed in claim 1, whereinthe base member has at one side a recess and wherein the clamping means for the backing strips comprise: a bolt device having at one end a clamping jaw which is located in said recess in the base member for engaging the adjacent backing strip and bringing lateral pressure to bear to clamp the strips in their adjusted position in the channel of the base member.

4. A dop or holder as claimed in claim l, wherein the clamping memberY for the upper side of the stone comprises a lever the forward endl of which has a cup and ball foot for engaging said upper side of the stone.

FREDERICK CHARLES JEARUM. 

